October 19, 2003, 06:55 PM
... how do they work? After I learn that, what are their advantages and disadvantages?
I've only ever bought Weaver-type rings/mounts. I did buy a used rifle once that had a scope that appeared to have been mounted to the front mount at 90 degrees to the barrel/receiver, then twisted back to the rear mount. Was this a "Double Dovetail?"
October 19, 2003, 08:36 PM
I did buy a used rifle once that had a scope that appeared to have been mounted to the front mount at 90 degrees to the barrel/receiver, then twisted back to the rear mount. Was this a "Double Dovetail?"
When you had to twist the front ring 90° to align the scope, the ring is what is termed 'Dovetailed' as the connecting portion of the ring that goes into the base (if taking a cross section of the ring) is dovetailed shaped, much like a dovetail joint of two wooden boards.
Since only the front had to be swiveled it would basically be a single dovetail. If both rings, front and back, had to be turned, they would be double or dual dovetail.
The single could be easier to mount as there is only one ring to turn and some folks, although it is not a good idea, IMO, use the mounted scope to torque the ring in. Now most modern scopes should be able to handle the stress, but why apply it when you don't have to. Personally, I don't like to abuse my equipment (take that any way you want to), and using the scope as a wrench is abuse, IMO.
The rear base of the single dovetail is normally an adjustable type that can apply some windage to the scope assembly by means of two bolts on each side of the bottom if the rings corresponding to the two fingernail nick notches on the lower ring.
The benefits of the single is that the rear is adjustable for windage. However, under heavy recoi, the base and rings provide very little support in keeping the rings and scope in place. Almost all of the stress from the recoil is taken by the dovetail of the front ring. This could eventually shear the bottom of the front ring over time.
With the dual dovetail, both rings take the stress. No additional windage adjustments to complement the scope's windage are provided by the rings.
With Weaver-types, generally, there is a portion of the bottom of the rings that go into the slots of the rail(s) and they absorb the stress of recoil. Usually, both Weaver-type rings are the same so both front and back take the stress much like the dual.
Some folks are more comfortable with duals and some are OK with singles. IMO, depends on what you're shooting. .375 H&H? Dual. .22 lr? Single is OK. I've used singles mostly in the past without any problems but i've only shot .308 Win at the most. I've converted to Leupold's QR setup nowadays, though, which act more like duals.
October 20, 2003, 08:31 AM
Thank you for that very lucid explanation. I understand it, and now I have an explanation for a couple of strange scope occurences. It requires a really large amount of windage to sight in this (old-style) Weaver K-4, and I had blamed the manufacturing. It now seems likely that the sccope was used as a lever on the install of the dovetail rings.
Fortunately, the new Weaver company has a program to replace the old scopes with ne-style scopes at a reasonable trade-in - 50% off the MSRP. While that's not great, I wouldn't be comfortable selling this scope to anybody, so I'll take advantage of their offer.